Alpha-picolinic acid activates diverse defense responses of salicylic acid-, jasmonic acid/ethylene- and Ca2+-dependent pathways in Arabidopsis and rice suspension cells

Alpha-picolinic acid (PA) is an apoptosis inducer in animal cells, and could elicit hypersensitive response (HR) in rice, a monocotyleclonous model plant. Here we report that PA is an HR inducer in plants. It induced HR in Arabidopsis, a dicotyledonous model plant, including the oxidative burst and cell death. We investigated defense signal transduction activated by PA through marker genes of particular defense pathways in Arabidopsis. The result indicated that both the salicylic acid-dependent and jasmonic acid/ethylene-dependent pathways were activated by PA, in which the marker defense genes PR-1, PR-2 and PDF1.2 were all induced in dose-dependent and time-course manners. We also observed that the PA-induced reactive oxygen species (ROS) production in rice suspension cells was Ca2+-dependent. Together with our previous studies of PA-induced defense activation in rice, we conclude that PA acts as a nonspecific elicitor in plant defense and has a potential utilization in cellular model establishment of systemic acquired resistance (SAR) activation.